Systems and methods for robotic sensing, repair and inspection

ABSTRACT

Various embodiments of a bio-inspired robot operable for detecting crack and corrosion defects in tubular structures are disclosed herein.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation patent application of U.S. Non-Provisionalapplication Ser. No. 16/844,519 filed on 9 Apr. 2020, now U.S. Pat. No.11,504,854, that claims benefit to U.S. Provisional Patent ApplicationSer. No. 62/831,268 filed 4 Apr. 2019, which is herein incorporated byreference in its entirety.

GOVERNMENT SUPPORT

The invention was made with government support under DE-FE0031649awarded by the US Department of Energy. The government has certainrights in the invention.

FIELD

The present disclosure generally relates to non-destructive testing(NDT); and in particular, to a bio-inspired robot for non-destructivetesting and inspection of tubular structures using multi-transducerimaging.

BACKGROUND

Tubular structures are commonly used in boilers and heat exchangers.Working under extreme conditions such as high temperatures, large stressloads, hot and high-velocity steam and pressure leads to corrosion,cracks, and stress-corrosion cracks in either the body or weldedconnections of these components. Regular inspection of these componentsis vital to avoid tube leakages. This task can be challenging,time-consuming and in many cases, impossible. Using robots forinspection is a promising solution to these challenges. Typical roboticsystems show limitation in interacting with complex environments,however, bio-inspired robotics systems have proven helpful in overcomingthese limitations. Tokay geckos, for instance, have one of the mosteffective and versatile attachment systems which enable them to attachquickly and reversibly to surfaces of varying chemistry and topography.

Detecting and characterizing corrosion and crack type defects on tubularstructures is one of the major problems faced by the power generationindustry. One approach for the measurement of remaining wall thicknessand crack detection is to use ultrasound. Contact ultrasound testing(UT) based on bulk waves is time-consuming and requires preparedsurfaces of adequate couplant for point-by-point scanning. Recentdevelopments in couplant-free UT may remove a need for couplant inultrasound technologies, and the development of advanced Lamb wave-basedimaging may eliminate the need for point-by-point inspection of thecross-section of a tubular structure.

It is with these observations in mind, among others, that variousaspects of the present disclosure were conceived and developed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present patent or application file contains at least one drawingexecuted in color. Copies of this patent or patent applicationpublication with color drawing(s) will be provided by the Office uponrequest and payment of the necessary fee.

FIG. 1 is a perspective view of one embodiment of a bio-inspired robot(e.g. lizard-inspired tube inspector (LTI) robot).

FIGS. 2A, 2B, and 2C are illustrations showing three different tubeconfiguration scenarios that the lizard-inspired tube inspector (LTI)robot may be operable to handle: a 180 degree elbow, a 90 degree elbow,and a flange, respectively.

FIG. 3A is an illustration showing a first embodiment of the gripperassembly of the lizard-inspired tube inspector (LTI) robot of FIG. 1 ;

FIG. 3B is an illustration showing a second embodiment of the gripperassembly of the lizard-inspired tube inspector (LTI) robot of FIG. 1 ;

FIG. 4 is an illustration showing one embodiment of the tail assembly ofthe lizard-inspired tube inspector (LTI) robot of FIG. 1 .

FIG. 5 illustrates helical paths between a pair of transducers/sensorson a tubular surface.

FIGS. 6A and 6B are graphical representations of multi helicalultrasound imaging (MHUI) for corrosion detection and evaluation on atubular surface using six omnidirectional Lamb wave transducers/sensors;FIG. 6A depicts helical paths between the six transducers and FIG. 6B isthe resulting MHUI image showing corrosion on the tubular surface.

FIGS. 7A and 7B are illustrative of Lamb wave-based total focusingmethod (TFM) for crack detection and evaluation; FIG. 7A is a photographof two clusters of transducers on an aluminum plate during experimentaltesting and FIG. 7B is the resulting Lamb wave-based TFM image depictinga crack in the aluminum plate.

FIG. 8 is an illustration showing data collection for MHUI and Lamb-waveTFM data as well as coverage area through one cycle of movement of thelizard-inspired tube inspector robot of FIG. 1 .

Corresponding reference characters indicate corresponding elements amongthe view of the drawings. The headings used in the figures do not limitthe scope of the claims.

DETAILED DESCRIPTION

A bio-inspired robotic device for detection and evaluation of crack andcorrosion defects in tubes is disclosed herein. In one embodiment, therobotic device includes a pair of gripper blocks, each gripper blockincluding a motor and a plurality of toes. Each of the plurality of toesincludes a network of couplant-free ultrasound transducers fornon-destructive testing of surfaces. In addition, each toe includesfrictional pads that can be used for effective climbing of tubes orother surfaces. In some embodiments, the pair of gripper blocks arelinked by a bendable “backbone” which is capable of elongation to allowthe robot to maneuver along pipes and surfaces. In some embodiments, therobotic device further includes a tail equipped with various transducersfor further examination of tube surfaces. Referring to the drawings,embodiments of the tube-inspector robotic device, herein referred to as“the robot”, are illustrated and generally indicated as 100 in FIGS. 1-8.

Robot Structure: Bio-Inspired Design

Referring to FIG. 1 , a robot 100 for inspection and repair of tubes isshown including a pair of dexterous gripper blocks 104, each gripperblock 104 having a plurality of toes 126. In some embodiments, each ofthe plurality of toes 126 is equipped with a friction pad 127 that cangrip tubular surfaces 10 of different sizes having smooth or corrodedsurfaces. The gripper blocks 104 are connected by a backbone 108 thatincludes a first linear actuator 142A and a second linear actuator 142Blinked by a rotational actuator 144. Referring to FIGS. 2A, 2B and 2C,the actuators 142 and 144 respectively enable forward/backward motion ofthe robot 100 and maneuvering on flanges, boiler walls, and elbows of45, 90, and 180-degree angles. In some embodiments, the robot 100includes a first and second motor 145A and 145B respectively engagingeach gripper block 104 with the first and second linear actuators 142Aand 142B. The first and second motor 145A and 145B serve to rotate eachgripper block 104 relative to the backbone 108.

Embodiments of the gripper block 104 are shown in FIG. 3A-3B, featuringa motor 124 surrounded by a housing 122. Each of the plurality of toes126 extend from an underside 129 of each gripper block 104. In someembodiments, each of the plurality of toes 126 includes the friction pad127 and a transducer 128. FIG. 3A shows one embodiment having each ofthe toes 126 including a first and second segment 126A and 126B linkedby a middle segment 126C. In an alternate embodiment shown in FIG. 3B,each of a plurality of toes 226 defines a curved profile. The curvedprofile includes a concave surface for engagement with a tubularstructure 10. The concave surface further includes the friction pad 227and the transducer 128. Referring to FIGS. 1 and 4 , the robot 100further includes a tail 106, shown in FIG. 4 , for additional stabilityand inspection. The tail 106 carries one or more transducers 130including a borescope 130A for tube inspection at desired locations thatmight be hard to access by the robot 100. In some embodiments, the tail106 includes one or more tail friction pads 137 for additional supportwhen climbing on tubular structures 10. The robot 100 includes one ormore onboard controllers programmed in C. However, depending on themission, data and power may be transmitted to/from the robot 100wirelessly or through a tether. A combination of machining and rapidprototyping techniques (e.g. 3D printing, laser cutting, and hybriddeposition manufacturing) are used for fabrication of the robot 100. Thegripper blocks 104 are fabricated using Hybrid Deposition Manufacturing(HDM) technique. The friction pads 127 are fabricated using softlithography with micro-scale feature (e.g. fibers) out ofPolydimethylsiloxane (PDMS) and Polyurethane. In some embodiments, shownin FIG. 1 , a camera 131 is installed on at least one of the gripperblocks 104 for visual inspection.

Couplant-Free Ultrasound Generation

Couplant-free ultrasound transducers 128 are placed on the toes 126 ofthe gripper blocks 104. Recent developments in couplant-free ultrasoundtechniques in addition to development of advanced Lamb wave-basedimaging remove the need for couplant and would also allow for inspectionof a line between two transducers instead of point-by-point inspectingthe cross section of a tube 10. To be able to use the toes 126 of thegripper blocks 104 as transducers, ultrasound waves need to transmitthrough the surfaces of the toes 126 with the friction pads 127.

Two separate sensing methods may be utilized for generating andreceiving Lamb waves: high-voltage ultrasound generation withpressurized contacted interfaces (achieved through the use of apiezoelectric transducer, which converts analog pressure into electricalsignals), and an Electro Magnetic Acoustic Transducer (EMAT). A materialand geometry of the friction pads 127 are optimized to maximize energytransmission. Ultrasound imaging based on guided ultrasound wavesprovides a unique solution to inspect a line between two transducers128A and 128B (FIG. 3B) instead of point by point inspection ofmaterial. This capability can be exploited in the case of cylindricalstructures (i.e. tubular structures 10) since theoretically there areinfinite helical paths (lines to be inspected) between the twotransducers 128, as illustrated in FIG. 5 .

Imaging: Corrosion and Crack Detection and Evaluation

Multi-transducer imaging approaches based on through-transmission andpulse-echo technique are considered to develop an imaging method usingthe data captured by the robot 100 across multiple positions of thegripper blocks 104. For example, at one location the gripper blocks 104may need to move and make different configurations. At eachconfiguration, one transducer 128A of the gripper block 104 will exciteguided ultrasound waves and another other transducer 128B will receivethe ultrasonic waves (FIG. 3B). This is repeated between each transducer128 in order to cover a large area of the tube 10. The robot 100 maychange the gripper 104 configuration to capture new sets of data. Animaging method based on guided wave total focusing method (TFM) andMulti-Helical Ultrasound imaging (MHUI) are used to detect and evaluatecrack and corrosion. The imaging methods are used as the robot 100 movesto construct images of the covered area. As shown in FIG. 8 , as therobot 100 progresses along the area, based on the new sets of data ateach new location, the images are updated. The transducers 128 do notneed to contact every single inch of the surface and can instead takeprocedural ultrasound images which cover a wider range, thus making theinspection rapid and versatile. An illustration can be seen in FIGS. 6Aand 6B where corrosion can be spotted using MHUI and 6 omnidirectionalLamb wave transducers. Lamb wave-based TFM (Total Focusing Method)creates an image for detecting cracks by combining the signals obtainedfrom multiple transmitters and receivers. Coverage of differentcombinations of the transducers was estimated for several crackorientations. Experimental tests were carried out on an aluminum plateinstrumented with two clusters of omnidirectional piezoelectrictransducers 128, as shown in FIG. 7A. Results demonstrate the efficacyof the proposed approach by identifying the simulated damage at thecorrect locations, as shown in FIG. 7B, where a crack in the aluminumplate can be identified using the TFM image. In some embodiments, therobot 100 simultaneously utilizes both MHUI and TFM imaging techniquesto process the information obtained by the couplant-free ultrasoundgenerators to detect and evaluate corrosion and cracks in tubularstructures, as shown in FIG. 8 .

In addition, the motion control of the robot 100 may be influenced by animaging algorithm in order to produce thorough images of problem areas.This is very important to consider that the location of the gripperblocks 104 can be controlled not only for stability and movement goalsbut also for inspection purposes.

While the robot 100 utilizes TFM and MHUI to obtain images of a tubularsurface, the method of sensing is not limited to Lamb-wave basedultrasound imaging. In some embodiments, the toes 126 of the gripperblocks 104 may be outfitted to use magnetic flux, eddy current orautomated visual inspection methods to determine defects in the tubularsurface 10. In the case of eddy current-based inspection, thetransducers 128 of the toes 126 of the gripper blocks 104 can bemodified or otherwise outfitted to detect eddy currents and variationsin eddy currents within the tubular surface 10. In other embodiments,the visual inspection can be performed using the borescope 130A alongwith the camera 131. In some embodiments, a magnetic gauss meter can beinstalled onboard the robot 100 for measuring magnetic field along thetubular surface 10.

In some embodiments, the robot 100 also includes repair equipmentincluding but not limited to welding or brazing equipment to mend cracksand other types of structural damage in copper or other types of tubingthat the tubular surface 10 can comprise. In other embodiments, therobot 100 includes equipment to repair composite structures such asfabric and resin. In some embodiments, each of the gripper blocks 104can be modified to heat surfaces for re-curing or bending.

It should be understood from the foregoing that, while particularembodiments have been illustrated and described, various modificationscan be made thereto without departing from the spirit and scope of theinvention as will be apparent to those skilled in the art. Such changesand modifications are within the scope and teachings of this inventionas defined in the claims appended hereto.

What is claimed is: 1-15. (canceled)
 16. A method, comprising:positioning a robot having a plurality of transducers on a surface;transmitting a plurality of subsonic signals through the surface usingthe plurality of transducers; receiving a plurality of feedback signalsfrom the surface using the plurality of transducers; and combining theplurality of feedback signals into an image.
 17. The method of claim 16,wherein the plurality of feedback signals are resultant of the pluralityof subsonic signals traveling through the surface.
 18. The method ofclaim 16, wherein the method is sequentially repeated by positioning therobot on a plurality of locations on the surface.
 19. The method ofclaim 16, wherein the image is produced from the plurality of feedbacksignals using a guided wave total focusing method.
 20. The method ofclaim 16, wherein the image is produced from the plurality of feedbacksignals using a multi-helical ultrasound imaging method.